In recent years, scientists and the public generally have become more accutely aware of the injurious effects of air pollution, and additionally, the contribution of the exhaust emissions of internal combustion engines to air pollution. Consequently, legislation of increasing restrictiveness has been passed to limit the exhaust emissions from automobiles. Although the automobile engine manufacturers have attained a certain degree of success in meeting these exhaust emission restrictions, it has been found in tests that an automobile which has met the requirements at the time of manufacture, often may not meet the requirements after only a relatively short periof of use. The expectancy that an automobile engine will meet the restrictive requirements diminishes with random, and often non-existent, maintenance efforts by the owner. Clearly, laxity of owner maintenance is in large part the result of the inconvenience connected with servicing of an automobile, prolonged waiting, and often, the deprivation of the use of the automobile. Without mandatory legislation regarding automobile maintenance, it is not expected that the maintenance efforts of automobile owners will significantly improve in the future. Consequently, the problem of maintaining an automobile engine in a low emissions condition after manufacture of the engine is a particularly perplexing one.
It is known that hydrocarbon emissions from the exhaust of automobile engines are in part the result of the existance of crevices in the combustion chamber where gasoline, liquid and vapor may find refuge from the burning process so that they are released to the atmosphere during the exhaust stroke as unburned hydrocarbons. Internal combustion engines which are not properly maintained develop deposits in the combustion chamber which greatly increase the number and size of crevices. To a lesser extent, a properly maintained engine will also develop deposits in the combustion chamber which results in increased unburned hydrocarbons.
The present invention provides a system for cleaning the combustion chambers to reduce the combustion chamber deposits in a manner which causes minimal, if any, inconvenience to the owner of the automobile, and which improves the operation of the engine so that the owner will be inclined to use the system. The system may be vehicle-mounted, and if desired, can be made automatic in operation so that no attention from the owner or user is required. Alternatively, an engine cleaning system according to the present invention can be adapted for use as a service station appliance, for example, by providing cooperating electrical fittings on the appliance and the automobile.
In one form of this invention, the ignition timing of selected cylinders of a multi-cylinder automobile engine is electrically advanced beyond the ordinary operating advances, and preferably, to such a degree to change the selected cylinders from power producers to power absorbers. The severe advance of those cylinders results in especially high combustion chamber surface temperatures and high detonation pressure which serve to burn and dislodge the combustion chamber deposits so that they are removed from the combustion chamber on the exhaust stroke. Since some of the cylinders operate as power absorbers, the throttle can be opened significantly above idle position so as to contribute to the high temperature and detonation pressures in the pre-ignited cylinders. By virtue of this feature, cleaning with advanced throttle opening can be accomplished with the transmission of the vehicle in neutral or disengaged from the engine without the use of a dynamometer or other power-absorbing device so that this system is especially adaptable to installation in the vehicle. Also, the period of operation is short so that the high temperatures are limited to the combustion chamber surfaces whereby the underlying material is not damaged by overheating. The selected cylinders which are advanced are changed at random or in sequence, automatically or manually, until all of the cylinders of the engine have been cleaned.
In one exemplary embodiment of a cleaning device of the present invention, a pulse derived from the automobile distributor contacts is received by a variable delay circuit which, in effect, provides an output pulse which may be variably advanced with respect to the ignition of the next cylinder. With four-cylinder systems conventional distributors and coils may be used since almost 90.degree. of supplementary advance is available which is adequate to cause the high surface temperatures and detonation pressures required for short period cleaning. In the case of engines having more than four cylinders, such as eight cylinder engine, the conventional distributor cap and coil is preferably substituted by an electronic distributor to provide the preferred degree of ignition advance.
Each of the systems disclosed herein may be readily modified to accommodate differing advances for the various cylinders to accommodate variations in fuel/air mixtures received by the cylinders. For example, the various cylinders may be adjusted in unison according to a single fuel air mixture signal, or the advance of the individual cylinders may be adjusted independently in accordance with plural fuel air mixture signals for respective ones or groups of the cylinders.
In yet another exemplary system, the occurrence of detonation or "pinging" is sensed and the advance of the particular cylinder experiencing detonation is retarded a fixed increment for each occurrence of detonation. When detonation is no longer detected at that cylinder, the timing of that cylinder is allowed to advance at a relatively slow rate until the next occurrence of detonation.
In another exemplary system, the time of flame propagation from the spark plug to a preestablished location in the cylinder combustion chamber is measured and the advance of the particular cylinder is set in accordance with the speed of propagation of the combustion flame relative to the engine cycle. It will be appreciated that each of the two latter systems are fully adapted to the conditions which affect engine operation, for example, the octane of the fuel being used, engine temperature and engine load.